Increased component concentration of iron nutrient solution

ABSTRACT

A solution suitable for application to plants and soil to correct iron deficiencies is described which comprises an aqueous solution of ferrous sulfate and mono-potassium or mono-ammonium hydrogen orthophosphate having an acidic pH value from about 1.5 to about 4, and wherein the components of the solution manifest a mutually increased solubility.

United States Patent Backlund [451 May 16, 1972 INCREASED COMPONENTCONCENTRATION OF IRON NUTRIENT SOLUTION Peter Stanley Backlund, Anaheim,Calif.

Union Oil Company of California, Los Angeles, Calif.

Filed: Nov. 12, I969 Appl. No.: 875,739

Inventor:

Assignee:

U.S.Cl ..71/34,23/l07,7l/l,

7l/64 C, 7l/63 Int. Cl. ..C05b 7/00 Field olSearcli ..7l/l,34, 63, 64C

Relerences Cited UNITED STATES PATENTS l/l942 Ellis et al ..7l/64 C XNikitin et al.

OTHER PUBLICATIONS Liquid Fertilizer Manual, 1967- Chapter 5, page 2; &Chapter 17, page I- published by National Fertilizer SolutionsAssociation, Peoria, lll.

Primary Examiner-Reuben Friedman Assistant Examiner-Bennett H. LevensonAttorney-Milton W. Lee, Richard C. Hartman, Lannas S. Henderson, DeanSandford, Robert E. Strauss and M. Dale Nelson 57 ABSTRACT A solutionsuitable for application to plants and soil to correct iron deficienciesis described which comprises an aqueous solution of ferrous sulfate andmono-potassium or mono-ammonium hydrogen orthophosphate having an acidicpH value from about 1.5 to about 4, and wherein the components of thesolution manifest a mutually increased solubility.

6 Claims, 2 Drawing Figures ma 7; H20

PATENTEDMAY 16 I972 m AAA/V m ZZZ @AWA W INVENTOR. in-W 5721/1/45) 5,467wiio BY all.

ATTORNEY INCREASED COMPONENT CONCENTRATION OF IRON NUTRIENT SOLUTIONDESCRIPTION OF THE INVENTION This invention relates to nutrientsolutions and in particular relates to iron-containing nutrientsolutions suitable for correction of iron deficiency in crops and soils.

One of the commonly encountered trace metal deficiencies in crops orsoils is an iron deficiency. While various solutions have been describedfor the preparation of iron-containing solutions for correcting suchdeficiencies, heretofore, no solution has been described which suppliesa mixture of nutrients comprising phosphorus in major quantities withlesser quantities of nitrogen, potassium, or mixtures thereof.

While the iron-containing solutions of this invention can be used tocorrect iron deficiencies at any time, it has been found that thesolutions are of particular value in late season application, i.e., 20to about 45 days prior to harvesting. It has been found that theapplication of these solutions, particularly those in which phosphorusis present in major proportions, results in greatly enhanced late seasongrowth, particularly when potassium or nitrogen are also present.Accordingly, this invention is directed to such iron-containingcompositions and a method for their preparation.

I have found that ammonium or potassium dihydrogen orthophosphate, ormixtures thereof, in admixture with ferrous sulfate in aqueous solution,from eutectic compositions having greatly enhanced solubilities of thesolids. This enhanced solubility greatly increases the amount of thephosphate, e.g., approximately doubles the solubility of the phosphatein the aqueous solution for any given salting out temperature. Thisenhanced solubility of a major nutrient in an iron-containing nutrientsolution is significant in that it permits the application of the majornutrient, i.e., phosphorus in substantial quantities to the plantsimultaneously with the application of the iron to correct irondeficiency.

The solutions of this invention will be described by reference to theFIGURES of which:

FIG. 1 is a ternary diagram of the system of mono-potassiumorthophosphate, water and ferrous sulfate; and

FIG. 2 is a ternary diagram for the system of mono-ammonium hydrogenorthophosphate, water and ferrous sulfate.

Referring to FIG. 1, it can be seen that the ferrous sulfate andmono-potassium hydrogen orthophosphate form eutectic compositions havinggreatly enhanced solubilities. The system depicted in FIG. 1 representsthe system at a pH value of 2; however, this system is substantiallyidentical to the systems having pH values in the range from about 1.5 toabout 4 which are encompassed within this invention. As illustrated, themaximum solubility of mono-potassium hydrogen orthophosphate in water atCentigrade is illustrated by point A as comprising about 18.5 weightpercent of the solids. At 20 C. there is a slight increase in solubilityto 23 weight percent solute as illustrated by point A,. Similarly, themaximum solubility of ferrous sulfate in an aqueous solution at 0 C. isapproximately 13 weight percent solute as illustrated by point B whileat 20 C. is approximately 18 weight percent solute as illustrated bypoint B,. The broken line A-B connecting the points A and B of the 0isotherm represents the normally expected solubilities of these saltsupon simple admixture of the solutions A and B. Thus, it would beexpected, absent any synergistic effect on solubility exhibited by thecombination, that the solubilities of the mixtures of the salts wouldfall along the straight line A-B. Contrary to this expectation, I havefound that the combination of salts exhibits a synergistic effect onsolubility and mixtures of the solutions A and B will dissolve furtherquantities of solutes so that the isotherm is substantially depressed,particularly for solutions containing about 2 to 4 weight percentferrous sulfate where, at point C, it can be seen that the total solutecontent of the solution is about 30 weight percent, considerably inexcess of the solubilities of either of the individual components in thewater. A similar effect can be illustrated at the 20 C. isotherm asrepresented by points A B, and C wherein a solution containing up to 38weight percent solute is possible without exceeding the 20 C. saltingout temperature.

Solutions falling within the scope of this invention therefore comprisethose solutions having salting out temperatures no greater than 0 C. andcomprising an aqueous solution of ferrous sulfate and mono-potassiumhydrogen orthophosphate with a pH value from about 1.5 to about 4 andthe composition included within the area defined by lines A-B, B-C andC-A of FIG. 1. Other solutions embraced within the scope of thisinvention comprise those solutions having from 1 to about 15 weightpercent ferrous sulfate, from 5 to about 34 weight percentmono-potassium hydrogen orthophosphate and from 62 to about weightpercent water, in an amount sufficient to provide a salting outtemperature of the solution from 0 to about 20 C. These compositions areencompassed within the shaded area defined by lines T-C, C-U, U-V, V-Wand W-C and C,-X appearing on FIG. 1. Of the solutions within the scopeof the invention, the most preferred are those containing from about 2to 10 weight percent ferrous sulfate with a consequentially high contentof mono-potassium orthophosphate.

Referring now to FIG. 2, the ternary system for the monoammoniumorthophosphate, ferrous sulfate and water can be seen; This system, asthat previously described, exhibits a eutectic point in solubility,i.e., the solutes exhibit synergistic solubilities. Thus themono-ammonium orthophosphate has a maximum solubility in an aqueoussolution at a pH from about 1.5 to 4 of about 26 weight percent at 0 C.and, at 20 C., approximately 40 weight percent. These points are shownas A and A of FIG. 2. As with the previously described system, thesolutions encompassed by my invention comprise those solutions containedwithin the area defined by the lines AB, B-B B,-C,, C -A and A -A. It isthese solutions which exhibit an unexpectedly low salting outtemperature for any given solute concentration which is lower than theexpected salting out temperature if the solutes simply combineadditively.

Particularly preferred solutions are those having from 1 to 16 weightpercent ferrous sulfate,from 10 to 55 weight percent mono-ammoniumorthophosphate and from 36 to about 78 weight percent water. Thesesolutions are shown in the shaded area of FIG. 2. Of these solutions andof the solutions within the area A-B-C-A, the most preferredcompositions are those having from about 2 to 10 weight percent ferroussulfate with consequentially high contents of mono-ammoniumorthophosphate.

Although not separately shown, similar ternary systems occur when theammonium or potassium dihydrogen orthophosphate solute is replaced witha mixture of both these solutes. Such systems, while being quaternarysystems, can be depicted on a ternary diagram at any constant ratio ofthe ammonium to the potassium salt and have solubilities intermediatethe two extremes shown in FIGS. 1 and 2.

The aforementioned solutions are employed with an acidic pH, i.e., a pHfrom 1.5 to about 4.0, preferably from 2 to 3. The dihydrogenorthophosphate solutes have a slightly acid pH when dissolved in anaqueous solution. Their pI-I, however, is lowered to the aforementionedvalues by the incorporation in the solution of a minor amount of amineral acid such as sulfuric acid, phosphoric acid, nitric acid, or ahydrohalic acid, e.g.,hydrochloric, hydrobromic, hydroiodic orhydrofluoric. Of the aforementioned acids, sulfuric and phosphoric arepreferred. The amount of the mineral acid which is added to thesolutions to lower the pH to the desired value can be from about 0.05 toabout 5.0 weight percent, preferably from about 0.1 to about 2 weightpercent.

The preferred use of the aforementioned solutions comprises the foliarapplication of the solutions to crops late in the growing season, e.g.,at a period within about 20 to 45 days prior to the harvesting. Thesolutions can be applied in undiluted concentration or, if desired, canbe admixed with from 0.1 to about 10 gallons of water per gallon of theaforementioned solution. The solutions are applied at a dosage suffivcient to provide from about 0.01 to about 0.5 pound iron per acre,preferably from about 0.1 to about 0.2 pound iron per acre. lnalternative applications, the solutions can be applied at theaforementioned dosages directly to the soil and can be applied at anytime prior to or during the growing season of the particular crop. insuch uses the solutions can be applied to correct known or suspecteddeficiencies of iron in the soil accharides such as melibose, maltose,revertose, celloboise, lactose or gentioboise; or trisaccharides such asrhamninose. Another group of suitable reducing agents are the variouspolyhydroxybenzenes such as hydroquinone, pyrogallol,

Solution Reducing agent 0.5 formaldehyd 0.3 pyrogallol. 0.3 glucose...

10.. 0.1 pyrogallol- 16.. 0.2 propionaldehyde 17.. 0.5 valeroaldehyde.-

18.. 0.1 pyrogallol 19.. 0.3 1,3,5-trihydroxy-benzene..-

.. 0.3 maltose before an iron deficiency appears in the crop or can beapplied to the soil whenever the iron deficiency becomes apparent by anabnormal appearance of the crop.

The aforementioned solutions are compatible with most nutrient solutionsand can be blended therewith in any desired proportion. -Thus theaforementioned solutions can be blended with from about 1 to aboutgallons per gallon of the solution of various nutrient solutions such asaqueous solutions of ammonium nitrate, urea, mixtures thereof, ureaformaldehyde solutions, ammonium phosphate solutions, etc. The aqueoussolutions can also be mixed with various suspensions of supersaturatedsolutions of the aforementioned nutrient solutes or suspensions ofvarious fertilizer solids such as triple superphosphate, superphosphate,acidulated and pulverized phosphate rock, etc.

It has been observed that the iron-containing solutions can develop aslight cloudiness upon standing. This is caused by the slow formation offerric orthophosphate which is insoluble in the aqueous solutions. Theferric orthophosphate is formed by a slow oxidation of the ferrous ionsto ferric ions by dissolved oxygen. This tendency does not provide anymajor problem in the use of the solutions because only a minor amount ofprecipitation occurs and the precipitate which is formed is flocculantand only imparts cloudiness to the solutions.

l have found that even this slight precipitation can be prevented byincorporating, in the solution, a soluble reducing agent that has anoxidation potential more negative than iron in the solution. Thepresence of from 0.1 to about 1.0, preferably from about 0.2 to 0.5weight percent of such a reducing agent maintains the clarity of thesolutions for prolonged storage periods. H

Examples of suitable reducing agents are the low molecular weight (C,Calkanals, e.g., formaldehyde, acetaldehyde, propionaldehyde,butyraldehyde, valeraldehyde, etc. Reduc ing sugars, e.g., those capableof reducing Fehlings solution, can also be used. Examples of these are:monosaccharides such as glucose, mannose, galactose, fructose orsorbose; dis- The aforementioned illustrative compositions are notintended to unduly limit the invention, but rather it is intended thatall obvious equivalents to such compositions which are described hereinor obvious equivalents of solutions described herein are within thescope of the invention.

I claim 1. An aqueous fertilizer solution comprising water, at least oneweight percent of ferrous sulfate solute, at least 5 weight percent of aphosphorus solute selected from the class consisting of mono-potassiumorthophosphate and mono-ammonium orthophosphate, and a sufficientquantity of mineral acid to impart said solution a pH of between about1.5 and 4; the concentration of said combined solutes in said solutionbeing (1) less than the salting out concentration at a temperature 20 C.and (2) greater than the additive concentrations of an aqueous solutionsaturated at 0 C. with said phosphorous solute, combined with an aqueoussolution saturated at 0 C. with said ferrous sulfate solute.

2. The solution defined in claim 1 wherein said mineral acid is nitric,sulfuric, or phosphorus acid.

3. The aqueous fertilizer solution of claim 1 wherein said phosphorussolute is mono-ammonium hydrogen orthophosphate.

4. The aqueous fertilizer solution of claim 1 wherein said phosphorussolute is mono-potassium hydrogen orthophosphate.

5. The aqueous fertilizer solution of claim 1 wherein said phosphorussolute is mono-potassium hydrogen orthophosphate and said combinedsolutes are present at a concentration greater than the saturatedconcentration of said solutes at 0 C. and less than the saturatedconcentration of

2. The solution defined in claim 1 wherein said mineral acid is nitric,sulfuric, or phosphorus acid.
 3. The aqueous fertilizer solution ofclaim 1 wherein said phosphorus solute is mono-ammonium hydrogenorthophosphate.
 4. The aqueous fertilizer solution of claim 1 whereinsaid phosphorus solute is mono-potassium hydrogen orthophosphate.
 5. Theaqueous fertilizer solution of claim 1 wherein said phosphorus solute ismono-potassium hydrogen orthophosphate and said combined solutes arepresent at a concentration greater than the saturated concentration ofsaid solutes at 0* C. and less than the saturated concentration of saidsolutes at 20* C.
 6. The aqueous fertilizer solution of claim 1 whereinsaid phosphorus solute is mono-ammonium hydrogen orthophosphate and saidcombined solutes are present at a concentration greater than thesaturated concentration of said solutes at 0* C. and less than thesaturated concentration of said solutes at 20* C.